Solar energy is a major lasting energy to human beings which is pollution free and clean, nowadays solar energy photovoltaic generating technology is one of the basic ways by which human beings get energy from the sun. The main criteria for evaluating advantage and disadvantage of a certain technical scheme of solar energy photovoltaic generating technology depends on the efficiency of the technical scheme in collecting solar energy per unit area on the earth. The efficiency of collecting solar energy per unit area on the earth specifically refers to that: the luminous flux value and light intensity value of sun light collected in unit time from a unit steradian at a certain location on the earth. For solar energy photovoltaic generating technology, the larger the luminous flux and light intensity of sun light with relative stable spectral frequency, the more advantages for photoelectric conversion system (such as solar cells) to generate increased quantity of optic-to-electric, and more electric energy can be obtained per unit area on the earth. This is due to the reason that: if the projection light projected on the photoelectric conversion system occurs photoelectric effect with its spectral frequency (or amplitude) being relative stable, the saturation value of the optic-to-electric strength generated will be in direct proportion to the luminous flux and light intensity of the projection light per unit area.
At present, the prior technical schemes of focusing solar energy by optical method are mainly schemes of light focused by the convex lens and light focused by the Fresnel lens, and other schemes utilizing different kinds of plane mirrors or parabolic reflectors, etc.
According to the prior schemes of light focused by the convex lens and light focused by the Fresnel lens, by using the light refraction characteristic of condensing lens, the sun light through lens area is refracted and focused to form a high temperature focal spot with high luminance nearby the lens focus. The area of condensing lens is much larger than that of the focal spot after light being focused, therefore, the solar energy collected per unit area can not be increased substantially by this kind of scheme; only the light intensity of focal spot is increased by the sun light through the lens area being refracted and focused. Although the used amount of solar cell can be reduced by this method, the focal spot formed after the sun light being refracted and focused by the condensing lens is in high temperature, with the photoelectric conversion efficiency of solar cell being inversely proportional to the temperature, cooling part is a must so that this kind of condenser-lens solar cells is able to maintain work efficiency and avoid being burnt, wherein the cooling part consumes certain amount of power, therefore, the efficiency-cost-ratio and cost performance of this kind of scheme are relatively low. Furthermore, the precondition of this kind of scheme is “light focusing”, the focal spot formed and the light intensity of the focal spot should be ensured, however, it is unable to adjust the distance between lens and collecting panel of solar cell to avoid happening of over-temperature.
For the prior schemes utilizing different kinds of plane mirrors or parabolic reflectors, the volume of light focusing system needs to occupy relatively large land area and space volume. Moreover, sun lights from different angles reached at different reflecting planes are reflected and focused together at a certain light focusing spot according to this scheme, which increases the sun light intensity of the spot, however, the total area of the reflecting planes in light-taking is far larger than the area of the light focusing spot. In conclusion, this kind of method can not substantially produce the effect of increasing the efficiency of collecting solar energy per unit area on the earth and the efficiency-cost-ratio and cost performance are relatively low.
Due to earth rotation and revolution around the sun, azimuth and declination angle change along with the daily movement of the sun in respect to a certain location on the earth. It is a must to have the light-taking plane of solar cell move all the time to track the sun so that more solar energy can be collected per unit time in the period of effective illumination time every day. Different kinds of sun-tracking methods of prior art mainly utilize measuring sensors (such as photosensitive sensor, heat sensitive sensor and temperature difference sensor, etc.) to induce sun light, then the measuring information is analyzed and processed by related devices, instructions are sent to servomechanism so that the mechanism moves accordingly to track the sun. The mechanism by this kind of method is complex in structure which consumes a certain amount of energy. Furthermore, devices by this kind of method are apparently limited by weather conditions (such as dark days with the sun can not be seen or the days when the sun covered by too many clouds), thereby mal-operations are likely to occur due to the low reliability and validity of the system. In addition, of the prior means of sun-tracking, there are devices utilizing computer compilation to preset programme so as to instruct the servomechanism to track the sun movement. The mechanism by this kind of method is also complex in structure which consumes a certain amount of energy, therefore, the efficiency-cost-ratio and cost performance are relatively low.
Obviously, in order to further develop solar energy photovoltaic generating technology for human beings, it is a must to change the light taking and focusing scheme of solar energy fundamentally by utilizing a more effective new way to increase the efficiency of collecting solar energy per unit area on the earth, and a concise and reliable new method is also needed to track the motion of the sun in two dimensions. The device product manufactured by the new technical scheme should have high efficiency-cost-ratio and cost performance so as to be widespread.
At present, human society consumes daily electric energy mostly on illumination (such as public facility illumination of street, park, public square and shop, etc, underground traffic illumination, illumination of residential area, corridor and family, etc.). Under the precondition that illumination effect and environment appearance are not affected, recycling the energy of different lamp lights by easy and effective means of light-taking and energy-collecting can save lots of energy with significant meanings which worth human society to pay high attention.